Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$207.62	5.240%	$218.4993	$218.50	$218.50	$218.50
Purchase #2	$14.34	9.566%	$15.7118	$15.71	$15.70	$15.70
Purchase #3	$86.82	3.250%	$89.6417	$89.64	$89.65	$89.60
Purchase #4	$38.31	9.267%	$41.8602	$41.86	$41.85	$41.90
Purchase #5	$24.55	11.248%	$27.3114	$27.31	$27.30	$27.30
Purchase #6	$51.25	12.755%	$57.7869	$57.79	$57.80	$57.80
Purchase #7	$154.40	7.378%	$165.7916	$165.79	$165.80	$165.80
7 purchase totals =	$577.29		$616.6029	$616.60	$616.60	$616.60